"Net earnings are calculated from gross earnings by deducting the employee's social security contributions and income taxes, and adding family allowances in the case of households with children. Income tax and social security contributions parameters refer to the beginning of the fiscal year, i.e. changes occurring later during the year are ignored. [..]
The data refer to an average worker at national level for different illustrative cases, defined on the basis of marital status (single vs. married), number of workers (only in the case of couples), number of dependent children, and level of gross earnings, expressed as percentage of the average earnings of an average worker (AW)."
(Eurostat, http://ec.europa.eu/eurostat/cache/metadata/en/earn_net_esms.htm, 16-01-2015)